For builders, framers & finish carpenters

The construction calculator that speaks your units.

Metric-first, flawless feet-and-inches. Type 5 ft 3 1/2 in one line on a keypad built for the trade, get every answer in both systems — and it all works fully offline, right on the slab.

100% offline on site No account, no sign-up Fractions down to 1/64"
Download on the App Store

Free to download · iPhone · Core calculators free forever

1/64" precision
round the way your tape reads
Airplane mode? Fine.
every calculator runs on-device
Both systems, every result
Metric-first with feet-and-inches that never round wrong. No mode switching mid-job.
16 trade calculators
Stairs, rafters, concrete, framing, tiling, decking — each with a clear diagram.
100% offline
No account, no sign-up, no signal needed. Works in airplane mode in the basement.
Built for the tape measure

A calculator that thinks in 5 ft 3 1/2.

Phone calculators think in decimals. Chalk thinks in feet, inches, fractions, and millimeters — the numbers you actually build with.

ftinn/d÷ 789× mcm1/16=

Purpose-built keypad

Type 5 ft 3 1/2 in one line — dedicated feet, inch, and fraction keys mean no decimal conversions in your head and no tapping through menus mid-measure.

16 trade calculators

Stairs, rafters & roof pitch, concrete, framing, drywall, tiling, brick & block, decking, balusters, aggregates and more — one app instead of a folder of them.

riserun

Clear diagrams, every time

Every calculator shows a labeled diagram of exactly what you're entering — rise, run, spacing, depth — so the number you type is the number you meant.

Deck — Johnson St 14 calcs
Basement stairs 6 calcs
Garage slab just now

Saved projects & recents

Every calculation lands in a history you can name and file by job. Yesterday's rafter length is one tap away — no re-measuring, no napkin math.

3' 5 37⁄64"
1/64 · 1/32 · 1/16 · 1/8

Precision you choose

Set fraction rounding to match the work — 1/8" for framing, down to 1/64" for cabinet and finish work. Chalk rounds the way your tape reads.

Airplane-mode proof

No account, no sign-up, no cloud. Every calculator runs entirely on your iPhone — in the basement, behind the shear wall, or forty minutes past cell coverage.

The toolbox

Every trade, covered.

Sixteen calculators, each with a diagram and dual-unit results.

Stairs Rafters & roof pitch Concrete slabs, footings & post holes Framing & studs Drywall Tiling Brick & block Board feet Decking Equal spacing & balusters Aggregates — gravel, soil & asphalt Area & volume Pitch & slope Check square (3-4-5) Unit converter Running measurements layout table

Highlighted calculators are free forever, along with the fraction calculator.

No wrong side of the tape

Metric first. Imperial fluent.

Plans in millimeters, lumber in feet? Chalk shows every result in both systems, side by side — no mode toggles, no conversion errors, no 16 mm mistakes.

  • Every result rendered in metric and feet-inch-fraction at once
  • Mix units inside one calculation — add 2.4 m to 3 ft 6 1/2
  • Fractions that stay exact, not floating-point approximations
  • A full unit converter for length, area, volume & weight, free
Rafter length
4.87 m
Same answer, your tape
15 ft 11 3⁄4 in
One calculation. Both systems. Every time — down to 1/64" when you need it.
Offline & private

Job sites don't have Wi-Fi.
Chalk doesn't need it.

Chalk is built like a tool, not a service — everything runs on your phone and stays there.

Works in airplane mode

Every calculator, diagram, and saved project works with zero signal — poured basements, remote lots, and steel buildings included.

No account, ever

No sign-up, no email, no password. Open the app and start measuring. Your projects and history live on your device, not on our servers.

No tracking across apps

No personal data collected, no IDFA, no ad tracking — just anonymous usage stats to make the app better. Read the privacy policy.

Pricing

Costs less than the pencil you lost today.

The core calculators are free forever. Chalk Pro unlocks the full trade toolbox.

Free forever
$0
no account, no time limit
  • Feet-inch-fraction calculator with the full keypad
  • Unit converter
  • Check square (3-4-5)
  • Pitch & slope
  • Area & volume
  • Metric + imperial results, everywhere
$17.99/yr ≈ $1.50/mo
Chalk Pro
$2.99/wk or $17.99/yr
auto-renewing · cancel anytime · handled by Apple
  • All 16 trade calculators
  • Stairs, rafters, concrete, framing, drywall, tiling
  • Brick & block, board feet, decking, balusters, aggregates
  • Running measurements layout table
  • Saved projects & full calculation history
  • Fraction precision down to 1/64"

Chalk Pro is an auto-renewing subscription billed to your Apple ID. There's no free trial — the free tier is simply free, forever. Cancel anytime in your iPhone Settings; you keep Pro until the end of the paid period. See the terms.

FAQ

Fair questions

What's free and what's Pro?
Free forever: the feet-inch-fraction calculator with the full keypad, the unit converter, check square (3-4-5), pitch & slope, and area & volume. Chalk Pro unlocks the other trade calculators — stairs, rafters & roof pitch, concrete, framing, drywall, tiling, brick & block, board feet, decking, equal spacing & balusters, aggregates, and the running measurements layout table — plus saved projects.
How does the subscription work?
Chalk Pro is $2.99/week or $17.99/year, auto-renewing, with all purchases handled by Apple through your Apple ID. There is no free trial — you're never charged unless you actively subscribe. Prices may vary by region and are always shown in the app before you confirm.
Can I cancel anytime?
Yes. Open iPhone Settings → your name → Subscriptions → Chalk, and tap Cancel. You keep Pro access until the end of the period you've already paid for, and you won't be charged again. No calls, no forms.
Does it really work with no signal?
Yes — completely. Every calculator, diagram, saved project, and setting runs on-device. Chalk needs the internet exactly once: to download it. After that, airplane mode is fine.
Can I mix metric and imperial?
That's the whole point. Every result is shown in both systems at once, and you can mix units within a single calculation — add 2.4 m to 3 ft 6 1/2 and read the answer off either scale. No mode switch buried in settings.
How precise are the fractions?
You choose the rounding: 1/8", 1/16", 1/32", or down to 1/64" for finish and cabinet work. Internally Chalk keeps fractions exact, so repeated additions don't drift the way decimal calculators do.
Can I rely on the results for a build?
Chalk's calculators are estimating tools. Always verify dimensions, quantities, and structural values against your plans, local codes, and a qualified professional before you cut, pour, or order materials — see the terms of use.

Measure twice. Calculate once.

Put a calculator in your pocket that reads the tape the way you do.

Download on the App Store

Free to download · core calculators free forever · works offline